How to use the numexpr.necompiler.ASTNode function in numexpr

def __eq__(self, other):
        if self.astType == 'alias':
            self = self.value
        if other.astType == 'alias':
            other = other.value
        if not isinstance(other, ASTNode):
            return False
        for name in self.cmpnames:
            if getattr(self, name) != getattr(other, name):
                return False
        return True

children += [ASTNode('raw', 'none',
                                         interpreter.funccodes[funcname])]
                    break
            else:
                raise NotImplementedError(
                    "couldn't find matching opcode for '%s'"
                    % (ast.value + '_' + retsig + basesig))
        # First just cast constants, then cast variables if necessary:
        for i, (have, want) in enumerate(zip(basesig, sig)):
            if have != want:
                kind = typecode_to_kind[want]
                if children[i].astType == 'constant':
                    children[i] = ASTNode('constant', kind, children[i].value)
                else:
                    opname = "cast"
                    children[i] = ASTNode('op', kind, opname, [children[i]])
    else:
        value = ast.value
        children = ast.children
    return ASTNode(ast.astType, ast.astKind, value,
                   [typeCompileAst(c) for c in children])

funcname = (ast.value + '_' + retsig + sig).encode('ascii')
                if funcname in interpreter.funccodes:
                    value = ('func_%sn' % (retsig + sig)).encode('ascii')
                    children += [ASTNode('raw', 'none',
                                         interpreter.funccodes[funcname])]
                    break
            else:
                raise NotImplementedError(
                    "couldn't find matching opcode for '%s'"
                    % (ast.value + '_' + retsig + basesig))
        # First just cast constants, then cast variables if necessary:
        for i, (have, want) in enumerate(zip(basesig, sig)):
            if have != want:
                kind = typecode_to_kind[want]
                if children[i].astType == 'constant':
                    children[i] = ASTNode('constant', kind, children[i].value)
                else:
                    opname = "cast"
                    children[i] = ASTNode('op', kind, opname, [children[i]])
    else:
        value = ast.value
        children = ast.children
    return ASTNode(ast.astType, ast.astKind, value,
                   [typeCompileAst(c) for c in children])

def precompile(ex, signature=(), context={}):
    """Compile the expression to an intermediate form.
    """
    types = dict(signature)
    input_order = [name for (name, type_) in signature]

    if isinstance(ex, (str, unicode)):
        ex = stringToExpression(ex, types, context)

    # the AST is like the expression, but the node objects don't have
    # any odd interpretations

    ast = expressionToAST(ex)

    if ex.astType != 'op':
        ast = ASTNode('op', value='copy', astKind=ex.astKind, children=(ast,))

    ast = typeCompileAst(ast)

    aliases = collapseDuplicateSubtrees(ast)

    assignLeafRegisters(ast.allOf('raw'), Immediate)
    assignLeafRegisters(ast.allOf('variable', 'constant'), Register)
    assignBranchRegisters(ast.allOf('op'), Register)

    # assign registers for aliases
    for a in aliases:
        a.reg = a.value.reg

    input_order = getInputOrder(ast, input_order)
    constants_order, constants = getConstants(ast)

raise NotImplementedError(
                    "couldn't find matching opcode for '%s'"
                    % (ast.value + '_' + retsig + basesig))
        # First just cast constants, then cast variables if necessary:
        for i, (have, want) in enumerate(zip(basesig, sig)):
            if have != want:
                kind = typecode_to_kind[want]
                if children[i].astType == 'constant':
                    children[i] = ASTNode('constant', kind, children[i].value)
                else:
                    opname = "cast"
                    children[i] = ASTNode('op', kind, opname, [children[i]])
    else:
        value = ast.value
        children = ast.children
    return ASTNode(ast.astType, ast.astKind, value,
                   [typeCompileAst(c) for c in children])

"""
    children = list(ast.children)
    if ast.astType == 'op':
        retsig = ast.typecode()
        basesig = ''.join(x.typecode() for x in list(ast.children))
        # Find some operation that will work on an acceptable casting of args.
        for sig in sigPerms(basesig):
            value = (ast.value + '_' + retsig + sig).encode('ascii')
            if value in interpreter.opcodes:
                break
        else:
            for sig in sigPerms(basesig):
                funcname = (ast.value + '_' + retsig + sig).encode('ascii')
                if funcname in interpreter.funccodes:
                    value = ('func_%sn' % (retsig + sig)).encode('ascii')
                    children += [ASTNode('raw', 'none',
                                         interpreter.funccodes[funcname])]
                    break
            else:
                raise NotImplementedError(
                    "couldn't find matching opcode for '%s'"
                    % (ast.value + '_' + retsig + basesig))
        # First just cast constants, then cast variables if necessary:
        for i, (have, want) in enumerate(zip(basesig, sig)):
            if have != want:
                kind = typecode_to_kind[want]
                if children[i].astType == 'constant':
                    children[i] = ASTNode('constant', kind, children[i].value)
                else:
                    opname = "cast"
                    children[i] = ASTNode('op', kind, opname, [children[i]])
    else: